fix: extracting counterparty information to fix webhook generation (#190)

### TL;DR

Extracted `CounterpartyInformation` into a separate reusable schema
component.

### What changed?

- Created a new schema component `CounterpartyInformation` that was
previously defined inline
- Updated references in the `Transaction` schema to use the new
component via `$ref`
- Applied these changes consistently across both the main OpenAPI file
and the modular component files

### How to test?

1. Validate that the OpenAPI spec still compiles correctly
2. Verify that API documentation renders the `CounterpartyInformation`
schema properly
3. Confirm that any endpoints using transactions with counterparty
information still function as expected

### Why make this change?

This refactoring improves the OpenAPI specification by:
- Promoting reusability of the `CounterpartyInformation` schema
- Making the schema more maintainable by defining it in a single
location
- Following best practices for OpenAPI schema organization
- Ensuring consistency if this schema needs to be referenced from other
components in the future

Author: pengying

mintlify/openapi.yaml

@@ -0,0 +1,7 @@
+type: object
+description: Additional information about the counterparty, if available and relevant to the transaction and platform. Only applicable for transactions to/from UMA addresses.
+additionalProperties: true
+example:
+  FULL_NAME: John Sender
+  BIRTH_DATE: '1985-06-15'
+  NATIONALITY: DE

openapi.yaml

@@ -47,13 +47,7 @@ properties:
     description: Optional memo or description for the payment
     example: 'Payment for invoice #1234'
   counterpartyInformation:
-    type: object
-    description: Additional information about the counterparty, if available and relevant to the transaction and platform. Only applicable for transactions to/from UMA addresses.
-    additionalProperties: true
-    example:
-      FULL_NAME: John Sender
-      BIRTH_DATE: '1985-06-15'
-      NATIONALITY: DE
+    $ref: ./CounterpartyInformation.yaml
 discriminator:
   propertyName: type
   mapping: